Short answers, pulled from the story.
Army Group E was created on the 1st of January 1943 from the 12th Army. It operated across the Eastern Mediterranean, including Albania, Greece, the Territory of the Military Commander in Serbia, and the Independent State of Croatia.
Army Group E's units carried out the massacres of Kalavryta and Distomo in Greece, the Chortiatis massacre in September 1944, and the Cephallonia Massacre in September 1943, in which over 5,000 Italian prisoners of war were executed following the disarmament of the Italian army.
The Cephallonia Massacre took place in September 1943 after German troops from Army Group E disarmed Italian forces following Italy's change of allegiance. German troops executed over 5,000 Italian prisoners of war.
After Romania fell to Soviet forces in the summer of 1944, Army Group E withdrew from the Greek islands and mainland. It was then forced through the mountainous terrain of southwestern Serbia, northern Montenegro, and southeast Bosnia toward Croatia, under constant attack by Yugoslav Partisans and with some British assistance in Operation Floxo.
On the day of surrender, the 8th of May 1945, most of Army Group E was still three days' march from the Austrian border. By the 15th of May, numerous units had escaped to Austria, but 150,000 German soldiers were captured by Tito's forces. The group then consisted of seven German divisions, two Cossack divisions, and nine Croatian divisions.
Kurt Waldheim served in the military administration of Thessaloniki as a member of Army Group E during World War II. He later became President of Austria and Secretary-General of the United Nations, and his wartime service became a significant public controversy.